Bagaméry K, Kovács L, Nyári T, Falkay G
Department of Obstetrics and Gynaecology, WHO Collaborating Centre for Research in Human Reproduction, Albert Szent-Györgyi Medical University, Szeged, Hungary.
Mol Hum Reprod. 1998 Apr;4(4):387-91. doi: 10.1093/molehr/4.4.387.
Alpha2-Adrenergic receptors and non-adrenergic imidazoline binding sites (IBS) in human placental membranes were investigated by means of the radioligands [3H]-RX 821002 and [3H]-RX 781094 (idazoxan) respectively. Human term placentae (38-40 weeks) were obtained immediately after vaginal delivery. The specific binding of the alpha2-subtype-selective [3H]-RX 821002 confirms the presence of alpha2-adrenoceptors in the human placenta, while [3H]-idazoxan binds to non-adrenergic IBS. The sites were characterized by displacement analyses with various imidazoline and non-imidazoline drugs. The presence of an endogenous ligand for IBS has not yet been demonstrated. Clonidine displacing substance (CDS) was recently identified as agmatine; it recognizes both alpha2 and imidazoline receptors. This phenomenon was studied in crude placental membranes. The studies revealed that: (i) alpha2-adrenoceptors coexist with non-adrenergic IBS in human placental membranes; (ii) there is a strong probability that alpha2-adrenoceptors and IBS are pharmacologically distinct; and (iii) agmatine binds to placental alpha2 and imidazoline receptors with different affinities.
分别使用放射性配体[3H]-RX 821002和[3H]-RX 781094（咪唑克生）对人胎盘膜中的α2-肾上腺素能受体和非肾上腺素能咪唑啉结合位点（IBS）进行了研究。足月人胎盘（38 - 40周）在阴道分娩后立即获取。α2亚型选择性[3H]-RX 821002的特异性结合证实了人胎盘中存在α2-肾上腺素能受体，而[3H]-咪唑克生则与非肾上腺素能IBS结合。通过用各种咪唑啉和非咪唑啉药物进行置换分析对这些位点进行了表征。尚未证实IBS内源性配体的存在。可乐定置换物质（CDS）最近被鉴定为胍丁胺；它能识别α2和咪唑啉受体。在粗制胎盘膜中对这一现象进行了研究。研究结果表明：（i）α2-肾上腺素能受体与人胎盘膜中的非肾上腺素能IBS共存；（ii）α2-肾上腺素能受体和IBS在药理学上很可能是不同的；（iii）胍丁胺以不同亲和力与人胎盘α2和咪唑啉受体结合。
